Knowledge of the presence of electromyographic (EMG) signals in the muscles of humans, and the change of these signals with muscle activity, spawned development of electronic devices and techniques for monitoring those signals for the evaluation of the muscles. Human musculature, however, involves many hundreds of muscles in various muscle groups, which interact to provide skeletal support and movement. Much of the recent development has been concerned with the techniques and/or devices for monitoring the signals, analyzing the information obtained and providing reliable and useful data for the patient or treating physician.
U.S. Pat. No. 6,004,312 of Dec. 21, 1999, hereby incorporated by reference herein shows an example of a system and method for sensing and monitoring EMG signals in a patient. U.S. Pat. No. 6,745,062 of Jun. 1, 2004, hereby incorporated by reference herein shows a further example of a system and method for sensing and monitoring EMG signals using a flexible and extensible EMG electrode array placed adjacent the back of a patient.
Each of these patents shows examples of systems operative to acquire data representative of the relative level of muscle activity across a two dimensional area. These systems employ an EMG electrode array comprised of a two dimensional grid of electrodes. These electrodes are placed in adhesive contact with the patient using an electrically conductive adhesive such as hydrogel.
The electrical signals are captured from each of the electrodes in the array. In one example embodiment, to quantify the relative level of muscle activity detected for each electrode, these systems calculate a root-mean-square (RMS) voltage between each pairing of adjacent electrodes. Data representative of the calculated RMS values for adjacent electrodes may be visually displayed in a two dimensional image. Such an image can be superimposed above different muscle groups to assist in diagnosing a pain causing condition being experienced by the patient.
However, the lower back of a human patient has 48 paired symmetric muscles. Correlating the data produced from an electrode array to various combinations of the muscles in the lower back of a patient may not reveal which condition is causing pain in the lower back of the patient. Thus there exists a need for a new method and system for analyzing EMG data acquired from a patient's back for purposes of making an accurate determination as to what pain causing conditions the patient may or may not have.